The present application relates generally to wind turbines and more particularly relates to noise attenuating systems for the reduction of noise produced during operation of wind turbine rotor blades.
During the operation of a wind blade with an airfoil-shaped section, the fluid, for example air, flows along the airfoil-shape forming a boundary layer. Generally the boundary layer is laminar in the proximity of a leading edge of the wind blade and transitions to a turbulent state over the body of the airfoil-shaped wind blade. During operation, the wind blade generates considerable noise, which is a major constraint in utilizing the wind turbines for power production as the noise may bother people in residential areas located nearby.
One cause of the noise generated during the operation of the wind blade is the interaction of a trailing edge of the airfoil-shaped wind blade with the turbulent flow in the turbulent boundary layer. A turbulent flow includes various groups of randomly oriented turbulent eddies of various sizes and intensities that are associated with a turbulent kinetic energy. Generally, the higher the turbulent kinetic energy associated with the turbulent eddies, and the closer the turbulent eddies are to a scattering edge, the higher the noise produced. Furthermore, groups of large eddies are associated with low frequency noise and groups of small eddies are associated high frequency noise. The distribution of eddy sizes, the proximity of eddies to scattering surfaces such as an airfoil, and the response of the human ear to noise determine perceived noise levels.
There is therefore a desire for a wind blade that generates less noise during operation while maintaining the aerodynamic performance of the wind turbine.